"Ovulationrates are lower among women with epilepsy than in the generalpopulation. It has been suggested that these low ovulation rates may bedue in part to menstrual cycles that are longer or shorter than normal,and that lack of ovulation may in turn correlate with increasedfrequency of seizures, but prospective data are lacking in thispopulation.'

Totest these suggestions, the researchers studied menstrual cycle length,ovulation occurrence and seizure frequency in 100 women. The frequencyof seizures during cycles with ovulation and cycles where no ovulationoccurred was compared in the 30 women who had at least one of each typeof cycle during the study.

Ovulationoccurred in 90 per cent of 26-32 day cycles, but declined steeply whencycles were either longer or shorter, occurring in less than 40 percent of either 23- or 35-day cycles. Seizures occurred on average aboutevery four days in ovulatory cycles, and every three days in cycleswhere ovulation did not happen.